<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <!-- 内部样式表 -->
     <style>
     /*标签选择器*/
     div{
        width: 100px;
        height: 100px;
        background-color: brown;
     }   
     span{width: 100px;
        height: 100px;
    background-color: blue;
    }
     </style>
</head>
<body>
    <div>块级元素</div>
    <h1>一级标题</h1>
    <h2>二级标题</h2>
    <h3>三级标题</h3>
    <h4>四级标题</h4>
    <h5>五级标题</h5>
    <h6>六级标题</h6>
    <p>段落标签</p>

<!-- 行内元素 -->
 <span>行内元素</span>
 <span>行内元素</span>
 <b>文字加粗</b>
<strong>文字加粗</strong>
<em>斜体标签</em>
<i>斜体标签</i>
<sub>下标</sub>
<sup>上标</sup>

<div>
    <span>行内元素</span>
</div>
</body>
</html>